3,609 research outputs found

    Cross-diffusion systems for image processing: II. The nonlinear case

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    In this paper the use of nonlinear cross-diffu\-sion systems to model image restoration is investigated, theoretically and numerically. In the first case, well-posedness, scale-space properties and long time behaviour are analyzed. From a numerical point of view, a computational study of the performance of the models is carried out, suggesting their diversity and potentialities to treat image filtering problems. The present paper is a continuation of a previous work of the same authors, devoted to linear cross-diffusion models. \keywords{Cross-diffusion \and Complex diffusion \and Image restoration

    An optimal transportation approach for assessing almost stochastic order

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    When stochastic dominance FstGF\leq_{st}G does not hold, we can improve agreement to stochastic order by suitably trimming both distributions. In this work we consider the L2L_2-Wasserstein distance, W2\mathcal W_2, to stochastic order of these trimmed versions. Our characterization for that distance naturally leads to consider a W2\mathcal W_2-based index of disagreement with stochastic order, εW2(F,G)\varepsilon_{\mathcal W_2}(F,G). We provide asymptotic results allowing to test H0:εW2(F,G)ε0H_0: \varepsilon_{\mathcal W_2}(F,G)\geq \varepsilon_0 vs Ha:εW2(F,G)<ε0H_a: \varepsilon_{\mathcal W_2}(F,G)<\varepsilon_0, that, under rejection, would give statistical guarantee of almost stochastic dominance. We include a simulation study showing a good performance of the index under the normal model

    Cyanide-modified Pt(111) : structure, stability and hydrogen adsorption

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    A.C. acknowledges the support of the DGI (Spanish Ministry of Science and Innovation) through Project CTQ2009-07017. W.S. acknowledges financial support by the Deutsche Forschungsgemeinschaft under Schm 344/40-1, Schm 344/34-1.2 and FOR 1376. W.S. and P.Q. thank DFG-CONICET International Cooperation and CONICET for continued support. E.P.M.L. and M.Z.-M. wish to acknowledge CONICET PIP: 112-200801-000983, Secyt UNC, Program BID (PICT 2006N 946), and PME: 2006-01581 for financial support. P.Q. acknowledges PICT 0737-2008. A generous grant of computing time from the Baden-Wuerttemberg grid is gratefully acknowledged. M.E.-E. acknowledges an FPI fellowship from the Spanish Ministry of Science and Innovation and an accommodation grant at the Residencia de Estudiantes from the Madrid City Council.Peer reviewedPostprin

    New Data on an Old Issue: The Evolution of Prices in Eighteenth-Century Buenos Aires

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    Almost twenty years ago, historian John Coatsworth called for the collection and publication of a reliable and dependable series of prices and salaries in Latin America in order to compile a critical set of data that would enable the comparison of the economic histories of different regions.1 Since then, little has been written about prices and salaries in Latin America, in particular concerning the colonial period. For the first time, accurate price data for the city of Buenos Aires during the eighteenth century are now available. The evolution of prices in Buenos Aires is analyzed by comparing the price of local and imported products. The general price index for the eighteenth century included herein demonstrate price trends over the long term, revealing that one of the peculiarities of Buenos Aires' economy was the fact that the rise in production grew parallel to the rise in population. Consequently, prices remained steady throughout the century. The new price data that has emerged places the current historiographical debates started in the 1980s in opposition to the classical historiography. Classical historians have stated that the policies applied in the last quarter of the eighteenth century marked a turning point in the region's economy.2 In this perspective, the creation of the Viceroyalty of the Río de la Plata (1776), which turned the city into the viceregal capital city, and the opening to Spanish imperial trade (1778) proved crucial. According to classical historians, both policies "released" the economic forces which had been restrained until then and thus fostered the region's growth. The data analyzed herein suggests a new interpretation of economic development of Buenos Aires in the eighteenth century, thus providing further evidence that the region's economic growth in terms of population and production started in the first half of the eighteenth century.Fil: Cuesta, Eduardo Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Interdisciplinario de Economía Política de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Instituto Interdisciplinario de Economía Política de Buenos Aires; Argentin

    Properties improvement of poly(o-methoxyaniline) based supercapacitors : experimental and theoretical behaviour study of self-doping effect

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    The support of this research by FAPESP (2011/10897-2, 2013/07296-2), CsF-PVE (99999.007708/2015-07), CAPES and CNPq is gratefully acknowledged. We also thank the University of Aberdeen for providing computational time on MaxwellPeer reviewedPostprin

    A white dwarf-neutron star relativistic binary model for soft gamma-ray repeaters

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    A scenario for SGRs is introduced in which gravitational radiation reaction effects drive the dynamics of an ultrashort orbital period X-ray binary embracing a high-mass donor white dwarf (WD) to a rapidly rotating low magnetised massive neutron star (NS) surrounded by a thick, dense and massive accretion torus. Driven by GR reaction, sparsely, the binary separation reduces, the WD overflows its Roche lobe and the mass transfer drives unstable the accretion disk around the NS. As the binary circular orbital period is a multiple integer number (mm) of the period of the WD fundamental mode (Pons et al. 2002), the WD is since long pulsating at its fundamental mode; and most of its harmonics, due to the tidal interaction with its NS orbital companion. Hence, when the powerful irradiation glows onto the WD; from the fireball ejected as part of the disk matter slumps onto the NS, it is partially absorbed. This huge energy excites other WD radial (pp-mode) pulsations (Podsiadlowski 1991,1995). After each mass-transfer episode the binary separation (and orbital period) is augmented significantly (Deloye & Bildsten 2003; Al\'ecyan & Morsink 2004) due to the binary's angular momentum redistribution. Thus a new adiabatic inspiral phase driven by GR reaction starts which brings the binary close again, and the process repeats. This model allows to explain most of SGRs observational features: their recurrent activity, energetics of giant superoutbursts and quiescent stages, and particularly the intriguing subpulses discovered by BeppoSAX (Feroci et al. 1999), which are suggested here to be {\it overtones} of the WD radial fundamental mode (see the accompanying paper: Mosquera Cuesta 2004b).Comment: This paper was submitted as a "Letter to the Editor" of MNRAS in July 17/2004. Since that time no answer or referee report was provided to the Author [MNRAS publication policy limits reviewal process no longer than one month (+/- half more) for the reviewal of this kind of submission). I hope this contribution is not receiving a similar "peer-reviewing" as given to the A. Dar and A. De Rujula's "Cannonball model for gamma-ray bursts", or to the R.K. Williams' "Penrose process for energy extraction from rotating black holes". The author welcomes criticisms and suggestions on this pape
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